The M1 itself is an SoC. It's composed of parts, however, which can stack.
Eg., just look at the M1 variations present atm: variable gpu cores.
The "chiplet" speculation is that given the M1's variable high-perf, low-perf and cpu cores, this can scale up.
Leaks at least are all pointing in a 32-core, Xeon-competitor direction. It is theoretically possible they could do the same with GPU count, and try to compete perhaps in the mid-pro gfx range.
Basically all silicon works like this. "Variable cores" actually means some cores are disabled. This is usually done to increase overall yields: chips with damage inside one of the cores can still be binned as the lower core count SKUs.
The "you can scale up" thing is actually just how e.g. Intel makes bigger monolithic chips (Xeon/HEDT) with the same or very similar cores as the desktop ones. Meanwhile AMD, actually using chiplets, can cheaply do something more like "scale out" in the sense that they put more of the exact same die on a package.
Eg., just look at the M1 variations present atm: variable gpu cores.
The "chiplet" speculation is that given the M1's variable high-perf, low-perf and cpu cores, this can scale up.
Leaks at least are all pointing in a 32-core, Xeon-competitor direction. It is theoretically possible they could do the same with GPU count, and try to compete perhaps in the mid-pro gfx range.